An informative article detailing everything you would want to know about Carbon fibers, including the global scenario and the Indian context!
Historical Perspective
The commercial production of carbon fiber can be traced to 1969, when Courtalds in the UK opened a 5 Tonnes a year plant to make staple fiber that had a Tensile Strength of 1900 Mpa and Modulus of 180Gpa. From the days of its origin the name carbon fibers has come to be synonymous with Aerospace and Aero Structures which still continue to be the most profitable sectors for Carbon fiber manufacturers worldwide.
Though the worldwide market size for carbon fiber products is difficult to estimate, research has indicated this to be between 34,000 – 35,000 MT as of 2009. Aerospace still remains a major contributor, accounting for 30% of the total sales volume and 50% of the total sales value. Not surprisingly, the pricing of carbon fibers and its availability over the years has been closely tied to the demands of the Aerospace Industry. This correlation has meant that carbon fiber suppliers have been very erratic with their pricing and supplies. Their inability to supply fibers to Industrial applications during periods of high demand from Boeing and Airbus has resulted in the Industry growing at a sluggish pace.
The barriers to entry into the Aerospace and Defense sectors still remain very high – Characterized by high capital investment, long qualification cycles and technology intensive processes make it a challenge to serve this industry. This dichotomy of needs between the producer and end users needs to end if we are to see mass scale commercialization of carbon fiber composites. It is also interesting to note that while the Aerospace sector contributes 30% of total sales, the Industrial composites segment, i.e. Wind, Infrastructure, CNG, Auto, etc contribute the remaining 70% and have been experiencing double digit growth.
The applications for carbon fibers on the Industrial side and the wide variety of products and composite manufacturing processes that are available provide an attractive option to composite fabricators in emerging markets to develop new and innovative products.
Zoltek was one of the first companies to understand these dynamics and break away from it to ensure market-driven fair pricing and sufficient availability to support Industrial applications. Today Heavy Tow, Standard modulus or commercial grade carbon fibers with their lower costs structures and excellent performance are opening new doors for composite manufacturing. For the purpose of this article the focus will be on Industrial applications and commercial grade carbon fibers.
Manufacturing Method
The raw material used to make carbon fiber is called the precursor. About 90% of the carbon fibers produced are made from Polyacrylonitrile (PAN). The remaining10% are made from rayon or petroleum pitch. All of these materials are organic polymers, characterized by long strings of molecules bound together by carbon atoms. The exact composition of each precursor varies from one company to another and is generally considered a trade secret. During the manufacturing process, a variety of gases and liquids are used. Some of these materials are designed to react with the fiber to achieve a specific effect. Other materials are designed not to react or to prevent certain reactions with the fiber. As with the precursors, the exact compositions of many of these process materials are considered trade secrets.
The process for making carbon fibers is part chemical and part mechanical. The precursor is drawn into long strands or fibers and then heated to a very high temperature with-out allowing it to come in contact with oxygen. Without oxygen the fiber cannot burn. Instead, the high temperature causes the atoms in the fiber to vibrate violently until most of the non-carbon atoms are expelled. This process is called carbonization and leaves a fiber composed of long, tightly inter-locked chains of carbon atoms with only a few non-carbon atoms remaining. The repeated heat treatments in a carbonization oven and the application of sizing and finishing complete the manufacturing process.
Global Scenario
Carbon fiber today has come to be accepted as an established material for sectors that demand high performance. With the ability to offer weight reduction, excellent strength & Stiffness, corrosion resistance and excellent fatigue properties, carbon fibers are increasingly becoming the material of choice for FRP’s. Although it cannot compete in terms of price with GRP (Glass reinforced plastics), it offers performance benefits that cannot be met with GRP. Well designed and thought out CFRP (Carbon fiber reinforced plastics) parts are today able to achieve cost structures similar to traditional GRP parts.
The current worldwide production of PAN based carbon fibers is estimated at 70,00MT out of which commercial grade carbon fibers constitute about 20,000MT. Toray is currently the market leader with around 35% of the installed capacity, closely followed by Zoltek with about 30% and Toho – Tenax. Other significant players include SGL, Hexcel, Cytec, Mitsubishi, etc. AKSA & Formosa are other new entrants into this market. Carbon fibers are broadly classified into 3 sections based n their modulus. Standard Modulus – Modulus <250 GPa, Intermediate Modulus – Modulus <350Gpa, High Modulus – Modulus >300. Further, small Tow or Aerospace carbon fibers are defined as having a filament count of less than 24,000 and Commercial grade carbon fibers are defined as fibers having a filament count of more than 24,000 filaments in a tow bundle. The difference between the two is essentially in the purity of the precursor and to an extent the processing technologies. Aerospace grade fibers offer better properties and are easier to use but much more expensive than commercial varieties. The economies of scale related to producing commercial grade carbon fibers make them cheaper and more attractive. Commercial grade carbon fiber from Zoltek is today available at $10/lb versus Aerospace grade carbon fibers from Toray, Hexcel and Toho – Tenax sometimes being 3 -4 time more expensive.
Europe and North America still account for about 50% of all the total carbon fiber consumption. Asia accounts for about 20% of the total consumption with China leading the pack by some distance. In terms of Industry, Aerospace accounts for about 25% of current carbon fiber consumption followed by wind energy at about 10%, Automotive 5% with Civil engineering, Sporting goods, Marine and other industrial application completing the pie. The share of Industrial applications – Wind Energy, Infrastructure and Pressure vessels is expected to grow at the rate of about 35% every year over the next 5 years.
Product Forms, Process options and Typical End Products
 | Continuous Tow | 3K,12K,24K,50K | Filament Winding Pultrusion | CNG Tanks, Pultruded Rod, Sporting goods etc. |
 | Prepreg Tapes | Different Resin Systems | Autoclave, Vacuum Bagging | Wind Energy, Aerospace, Sporting goods |
 | Chopped Fibers | Different Lengths | Injection molding, SMC, BMC, LFT. Compression Molding | Automotive, Electrical components. Static Dissipation |
 | Milled Fibers | Injection molding, Dispersion | Buoyancy modules, Static Dissipation etc | |
 | Uni Directional & Multi Directional Fabric | 100 – 900GSM | Infusion, VARTM, RTM | Wind Energy, Automotive, Structural applications |
 | Woven Fabrics | Different weave patterns | Infusion, VARTM | Automotive, Secondary reinforcement. Industrial. |
A wide variety of Intermediate carbon fiber product forms are today available for processing into composites. The usage of Prepregs and Uni Directional fabrics remains to be very high. Chopped carbon fibers are increasingly finding their way to Thermoplastic and Thermoset application for Automotive structural or inner body components. The usage of carbon fiber tow for filament winding applications is well documented and used to manufacture a variety of products from rocket motor casings to CNG pressure vessels. Hybird product forms like +/-45, 0/90 Non Crimped Mutidirectional fabric, tri axial fabrics, SCRIM’s, Carbon non woven felts, Tri axials fabrics and Carbon – Glass Hybrid fabrics are also available for specialty applications. The gamut of available products today allows composite manufacturers to pick from a wind range of intermediate product forms as suitable to their application.
The Indian Context
The domestic market for carbon fibers has remained virtually stagnant due to poor availability, high prevailing prices and lack of support from carbon fiber manufacturers. The consumption of carbon fibers in India is estimated at around 50MT and this has largely been driven by the Defense and Aerospace sector. The lack of guidance in terms of choosing the right material, right processing technology and limited carbon composite design expertise has resulted in decimal level growth in the Indian market. In terms of carbon fiber usage India remains an aberration to the world standard. However, it is safe to believe this trend is set to change – A large part of this change will be driven by the needs of the Wind energy industry and the CNG pressure vessel market. The infrastructure and Automotive sectors are also beginning to move towards understanding and utilizing large volumes of carbon fiber composites. That said, apart from a few large technically capable organizations in India most fabricators remain low tech, relying on Hand lay up and infusion as primary molding technologies. For these SME’s to become a part of the mainstream there has to be a rapid movement towards advanced processing technologies like VARTM, prepreg and filament winding. Companies worldwide engaged in the use and manufacture of composite are today looking at India as a manufacturing base and to be a part of this global growth organizations must push towards developing better processing capability, design capability and testing facilities. The cost barrier can only be breached when companies are willing to invest in R&D. With companies such as Zoltek, Toho, Toray looking at India as a potential market the fiber availability situation is hopefully set to improve. The presence of large multinationals such as Bombardier, Boeing, Caparo Composites, Vestas, etc will only enhance the knowledge base and provide a technically competent workforce that this industry desperately needs.
Manufacturing process in 2010 – Composites applications in 2010 –
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